Customized fetal growth standard compared with the INTERGROWTH-21st century standard at predicting small-for-gestational-age neonates.

INTRODUCTION: The INTERGROWTH-21st project (IG-21) was recently performed aiming to provide a universal benchmark for comparing fetal growth across different ethnicities. Our aim was to compare the IG-21 with a customized standard for predicting pregnancies at risk for neonatal small-for-gestational age (SGA) and adverse outcomes.

MATERIAL AND METHODS: This was a prospective cohort study including singleton pregnancies presenting for fetal growth assessment between 26 and 36 weeks of gestation. Fetal growth restriction was defined as estimated fetal weight <10th centile for gestational age using IG-21 and a customized standard. Neonatal SGA was defined as birthweight <10th centile for gestational age by the Alexander chart. Primary outcome was the prediction of neonatal SGA. Secondary outcomes included a composite of adverse neonatal outcomes. The discriminatory ability of each growth standard was compared using area under receiver operating characteristic curves (AUC).

RESULTS: Of 1054 pregnancies meeting the inclusion criteria, the incidence of neonatal SGA was 139 (13.2%), and a composite adverse neonatal outcome occurred in 300 (28.4%). The sensitivity of the customized standard (38.8%) was higher than that of IG-21 (24.5%) for predicting neonatal SGA, with AUC (95% CI) of 0.67 (0.63-0.71) for customized vs 0.62 (0.58-0.65) for IG-21; P = .003. Both standards were comparable in predicting the composite adverse neonatal outcomes: AUC (95% CI) 0.52 (0.50-0.55) for customized vs 0.51 (0.50-0.53) for IG-21; P = 0.25.

CONCLUSIONS: Both growth standards had modest performance in detecting neonatal SGA and were poor at predicting short-term adverse neonatal outcome.